In numerous situations, it may be necessary to displace one or more mobile entities, manually or automatically, in liaison with a computer system, the latter preferably being capable of detecting the position and/or the orientation of those mobile entities.
Thus, for example, in a game utilizing figurines on a game board, enabling a user to play against a virtual player simulated by a computer system, the application implemented on the computer system must know the position of all the figurines of the game board, in particular those moved by the user, to calculate its move and make it possible to perform or indicate the displacements of the figurines.
There are solutions for detecting the position and/or the orientation of real objects on a game board making it possible to use those objects as an interface for a computer system.
Thus, for example, resistive type touch screens may be used as a game board in order to detect the position of an object such as a stylus when sufficient pressure is applied. However, this type of screen in general only supports a single contact and requires constant pressure by the user to know the position. In other words, it is not possible to detect the position of the stylus if the pressure applied by the latter is relaxed.
It is also possible to use capacitive type touch screens, based on the principle of a leakage of current through a conductive body. However, only objects that are conductive and linked to a ground enable the detection of their position. Thus, for example, the positions of objects of plastic or wood cannot be determined using such screens.
In general terms, the solutions based on touch screens, or touch film, only support a limited number of simultaneous or almost simultaneous touches and do not enable the determination of a high number of objects.
Other solutions implement technologies based on infrared, in particular in the form of tables. Thus, for example, the products known under the names Surface (Surface is a trademark of Microsoft), mTouch (mTouch is a trademark of Merel Technologies) and Entertaible (Entertaible is a trademark of Philips) use infrared cameras disposed within the thickness of the table. However, the required thickness of these tables makes them bulky and of low mobility and gives them a certain rigidity. Furthermore, their price does not really allow for family use.
Lastly, another solution developed by the Applicant enables real-time interfacing of a plurality of mobile entities with a computer system. After having selected at least one location module integrated in a mobile entity, this location module is activated sequentially. A signal is then received from this activated location module and information on position of the mobile entity comprising that activated location module is computed in real time from the received signal. The location modules are sequentially activated, a single location module being activated at a given time.
Furthermore, solutions exist for automatically displacing mobile entities from a first position to the second position. For these purposes, the mobile entities are typically provided with sensors and with motors actuating wheels. It is noted here that the use of motors to actuate wheels leads to a degree of precision of the movements. The sensors do not need to be very accurate.
To control the displacement of these mobile entities, PID type controllers may be used (PID standing for proportional-integral-derivative). It is to be recalled that a PID controller enables real-time computation of a difference between a real path of an mobile object and a desired path in order to adapt an actuator control to modify the direction of the object accordingly. These computations are generally carried out several times per second.
However, although such solutions may be satisfactory in certain conditions, they nevertheless have numerous drawbacks. To be precise, they are in particular often costly to implement and have mechanical weaknesses linked to the wear and clogging of the mechanism (for example tires, gear trains and wheel shafts).
The invention enables at least one of the problems set forth above to be solved.